To enhance grinding when the materials to be ground are of heterogeneous grain sizes, it is proposed (French patent No. 91.09788) to give the roller and/or the track a profile such that the gap between the roller and the track decreases progressively or by degrees from one edge of the track to the other.
The object of the present invention is to enhance the efficiency of the grinders of this type and to achieve a better distribution of the mechanical stresses in the roller and the track.